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Contaminants of concern at this site were selected from those chemicals for
which the concentration in at least one environmental medium exceeded a health-based
and medium-specific comparison value. Lifetime exposure to chemical concentrations
at or below the appropriate comparison values for a chemical is not expected
to result in more than 1 excess case of cancer in 1 million people exposed or
any noncancer health effects. Comparison values used in this assessment include
the following, developed by the Agency for Toxic Substances and Disease Registry
(ATSDR) and the Environmental Protection Agency (EPA):

If a chemical is found in a medium for which no comparison values exist, or for which there is no CREG available for a carcinogen, the chemical is retained as a contaminant of concern.

To identify chemicals that might contribute to the environmental contamination
at the North Bronson Industrial Area (NBIA) site after industrial releases in
the site area, the Michigan Department of Public Health (MDPH) searched the
Toxic Chemical Release Inventory (TRI) data base for 1987 through 1993. EPA
compiles the TRI from information provided by industries. The TRI contained
entries for two facilities with the same postal ZIP Code as the NBIA site, the
Bronson Plating Company facility and one identified as Kuhlman Plastics Group
(1987-1989) or Solvay Automotive Inc. (1990-1992). Both facilities are located
within the site study area.

Bronson Plating reported releases to the air of sulfuric acid, hydrochloric
acid, nickel, and chromium. They released copper, nickel, and chromium to the
water of Swan Creek (1987-1990) and County Drain # 30 (1991-1993). They also
reported use, but no environmental releases or transfers to other disposal facilities,
of phosphoric acid and sodium hydroxide (solution).

Kuhlman Plastics Group or Solvay Automotive Inc. reported releases to the air
of ammonia and sulfuric acid. They also reported transfers to the Bronson Wastewater
Treatment Plant, with no environmental release, of ammonium sulfate (solution)
and ethylene glycol.

Chromium, copper, and nickel, released by the Bronson Plating facility, are
included as contaminants of concern based on the previously mentioned criteria.
The other chemicals reported as released by the facilities are highly volatile
and do not tend to persist as environmental contaminants.

Unless otherwise cited, data in this public health assessment was taken from
the remedial investigation (RI) report (1). Contaminants
of concern at this site are listed in Table 1.

For this assessment, samples collected within the site study area are considered on-site samples.

Groundwater -- Private and Municipal Wells

On many occasions since 1974, various environmental and health agencies have
collected samples of water from private residential wells located within the
NBIA site study area. A total of four wells have been sampled (RW-1 through
RW-4 in Figure 2), but not all at any one
time, and the analyses performed varied from agency to agency and time to time.
The chronology of the private well sampling, both within and around the site
study area, is summarized in Table 2. A cross-reference
list between this assessment and the numbering systems in the RI report (Reference
1) is given in Table 3.

In 1974, samples of water from a private residential well south of the western lagoon area (RW-1
in Figure 2) contained approximately 5,000 parts per billion (ppb) each of acetone and methyl
ethyl ketone (MEK).5 Water from dewatering wells for construction at the Bronson municipal
Wastewater Treatment Plant, southeast of the west (old) lagoons and northeast of RW-1 (Figure 2), also contained acetone and MEK, at concentrations of approximately 1,000 ppb.

In October 1984, the MDPH Division of Water Supply6 collected a water sample from a private
residential well in the site study area (RW-2 in Figure 2), and analyzed the sample for bacteria,
VOCs, cyanide, and metals. None of these parameters were detected in the analysis (6).

In September 1988 and September 1989, the Michigan Department of Natural Resources,
(MDNR's) RI contractors collected samples from a residential well (RW-2, see
Figure 2) and a municipal well (PW-3) within
the boundaries of the NBIA site study area, analyzing the samples for a full
range of organic and inorganic chemicals. No organic chemicals or other contaminants
attributable to the site was detected in the samples from these wells. The samples
did contain low concentrations of several metals that are considered contaminants
of concern at the site (Table 4), but these
concentrations were generally comparable to background levels.

In December 1988, the MDPH collected a water sample from a private well located within the
site study area (RW-3, next door to RW-2, see Figure 2). This sample contained 457 ppb
trichloroethylene, 24 ppb cis-1,2-dichloroethylene, 1 ppb trans-1,2-dichloroethylene, 6 ppb vinyl
chloride, and 2 ppb 1,1-dichloroethylene.7 The residence served by RW-3 was later connected to
the municipal water system, and the well abandoned (7). The residence burned down in 1992
and has not been rebuilt as of this writing.

In January 1989, the MDPH collected additional water samples from RW-1 and RW-2. They
found no organic chemicals in either sample, and did not analyze them for any inorganic
contaminants of concern (7). In February 1990, the MDPH collected a sample of water from
Bronson Municipal Well PW-3, within the site study area. The sample contained no organic
chemicals but did contain 120 ppb manganese, a concentration higher than the ATSDR
comparison value (50 ppb) and higher than background levels (1). In July and October 1993, the
MDPH collected samples from RW-2 and one other residential well (RW-4, see Figure 2) within
the site study area. These samples contained trichloroethylene (up to 82 ppb) and traces of 1,1,1-trichloroethane (up to 0.7 ppb).8 Both residences have since been connected to the municipal water system.

Groundwater -- Monitoring Wells

In 1974, water from dewatering wells around construction at the Bronson Wastewater
Treatment Plant, located adjacent to the west lagoons in the site study area,
contained approximately 1,000 ppb of acetone and methyl ethyl ketone. Water
samples collected in 1979 from monitoring wells around the western lagoons contained
trichloroethylene (TCE) and heavy metals (Table
5). Groundwater samples collected in 1981 from monitoring wells around the
eastern lagoons and Bronson Plating contained TCE, chloroform, and heavy metals
(Reference 1, concentrations not cited).

MDNR's RI contractors collected samples of groundwater from monitoring wells
in the site study area in 1988, 1989, and 1991. Concentrations of contaminants
of concern are summarized in Table 5. They
found a plume of chlorinated ethylenes (vinyl chloride, 1,1-dichloroethylene,
1,2-dichloroethylene, and trichloroethylene) under much of the site study area.
The highest concentrations (up to 70,200 ppb total) were found under the former
Scott Fetzer Components Corporation plant in the southern section of the area.
Lower concentrations of these chemicals (100-1,000 ppb) were found in the groundwater
under the lagoon areas. Elevated concentrations of metals were found in several
isolated plumes, including one under each of the lagoon areas (cadmium, cyanide,
manganese, and nickel under the eastern lagoons; cadmium, cyanide, lead, manganese,
nickel, and zinc under the western lagoons) and a cyanide plume along Mill Street.
The two private wells (RW-2 and RW-4) where trichloroethylene was found in the
1993 MDPH sampling are within the organic plume, close to the area where the
maximum concentration was found in the monitoring wells.

Surface soil

During the RI investigation in 1991, the MDNR's contractors collected samples
of surface soil, 0 to 6 inches deep, from a ball field on the east side of the
site area (a background sample), the vacant L.A. Darling site, the former Scott
Fetzer Components Corporation plant, and the "Cyanide Destruction"
facility. The concentrations of contaminants of concern found in these samples
are summarized in Table 6. Most of these contaminants
were heavy metals, with the highest concentrations primarily found in samples
from the former "Cyanide Destruction" Facility.

Subsurface soil

During the RI in 1988, the contractors collected samples of subsurface soil from the berms
between the lagoons (Table 7). In 1989, the contractors collected soil samples from borings near
the eastern lagoons, and from monitoring well borings throughout the site (metals analyses only)
(Table 8). In 1991, they collected soil samples from borings located throughout the site study
area (also in Table 8). The highest concentrations of polycyclic aromatic hydrocarbons (PAHs)
were found in the shallowest samples (1 foot depth) from three borings located northeast of the
L.A. Darling site. The arsenic, beryllium, manganese, thallium, and vanadium concentrations
from 1989 listed in Table 8 were all from one sample, from 10 feet down in a boring for a
monitoring well south of the western lagoons. A duplicate of this sample contained much lower
concentrations of these metals (6.4 ppm vs. 95.9 ppm, not detected at 0.26 ppm vs. 157 ppm, 353
ppm vs. 5,160 ppm, not detected at 0.24 ppm vs. 19.4 ppm, and 9.2 ppm vs. 84.9 ppm,
respectively) and substantially different concentrations of other metals. The 1989 concentrations
of cadmium, chromium, cobalt, copper, nickel, and zinc listed in Table 8 were all from a single
sample, collected 10 feet below the surface near the eastern lagoons.

Lagoon surface water and sludge

MDNR's RI contractors collected samples of surface water from the western lagoons
and samples of sludge from the eastern lagoons in 1988. They collected sludge
samples from the western lagoons in 1989 and an additional water sample from
the western lagoons in 1991. Concentrations of contaminants of concern found
in these samples are summarized in Table 9
(water) and Table 9 (sludge). The contaminant
concentrations in sludge samples from the eastern lagoons were substantially
higher than those in sludge from the western lagoons.

On many occasions since 1984, various environmental and health agencies have collected
samples of water from private residential wells located near the NBIA site study area. A total of
19 wells have been sampled (RW-5 through RW-23 in Figure 2), but not all at any one time and
the analyses performed varied from agency to agency and time to time. The chronology of the
private well sampling is summarized in Table 2. A cross-reference list between this assessment and the numbering systems in the RI report (Reference 1) is given in Table 3.

In October 1984, MDPH collected water samples from three private residential
wells near the site study area, one to the west (RW-5 in Figure
2) and two north (RW-6 and RW-7). They analyzed the samples for bacteria,
VOCs, cyanide, and metals. None of these parameters were detected in the analysis
(6).

In September 1988 and September 1989, MDNR's RI contractors collected samples from four
residential wells in the site vicinity, RW-5, RW-6, RW-7, and one south of the site study area
(RW-8), and analyzed the samples for a range of organic and inorganic chemicals. No
contamination attributable to the site was detected in these wells. The samples did contain low
concentrations of several metals that are considered contaminants of concern at the site (Table 11), but these concentrations were generally comparable to background levels.

In January 1989, the MDPH collected water samples from RW-8 and from four other
residential wells in the site vicinity (RW-9 through RW-12), analyzing the samples
for VOCs and general chemical parameters. In July 1993, MDPH collected water
samples from RW-8, RW-9, RW-10, and five more residential wells near the NBIA
site (RW-13 through RW-17), analyzing the samples for VOCs. In July 1995, the
Branch County Health Department and the MDPH collected water samples from 14
private wells near the NBIA site study area, including RW-5, RW-8, RW-9, RW-10,
RW-11, RW-13, RW-14, RW-15, and 6 new wells (RW-18 through RW-23), analyzing
the samples for VOCs. None of these samples contained any VOCs and they were
not analyzed for any inorganic chemicals of concern at the site (7).
In August 1995, MDNR collected water samples from RW-6, RW-7, and six private
wells along Burr Oak Road, northwest of the site (RW-24 through RW-29), analyzing
the samples for VOCs, metals, and cyanide. These likewise did not contain any
VOCs. They did contain low concentrations of some metals that are contaminants
of concern at the NBIA site (Table 11) (8).

Groundwater -- Monitoring Wells

MDNR's RI contractors constructed monitoring wells north and south of the site study area to provide background samples of groundwater. They sampled these wells in 1989 and 1991. No organic chemicals were found, and the concentrations of metals found are summarized in Table 12.

Surface soil

In 1991, MDNR's RI contractors collected four samples of surface soil (to 6
inches deep) from areas southwest and north of the site to provide background
data (Table 13). These concentrations were
generally within the range of concentrations found in Michigan (9)
and the Eastern United States (10).

Subsurface soil

In 1989, MDNR's RI contractors collected samples of soil at 5-foot depth from
the borings for the off-site monitoring wells, and analyzed the samples for
metals (Table 14). Again, these concentrations
were generally within the range of concentrations found in Michigan (9)
and the Eastern United States (10).

Surface water and sediment

Samples of sediment collected in 1979 from County Drain #30 contained elevated
concentrations of polychlorinated biphenyls (PCBs) downstream from the western
lagoons (Reference 1, concentrations not cited).
MDNR's RI contractors collected sediment and surface water samples from County
Drain #30 upstream from the site, adjacent to the site, and downstream from
the site in 1988 and 1991. Concentrations of contaminants of concern in these
samples are summarized in Table 15 (sediment)
and Table 16 (surface water). They found
some chemicals at elevated concentrations in the samples collected adjacent
to the site, but none significantly elevated either upstream or downstream.
The PAH concentrations in sediment samples collected adjacent to the site were
generally within the range found in urban soils (Reference 11,
Table 5-2). In 1991, they also collected samples of water from several outfalls
into the drain from the site area. The outfall samples contained more chromium,
1,2-dichloroethylene, TCE, vinyl chloride, and PAHs than did samples from the
creek upstream of or at the site (Table 16).

In preparing this Health Assessment, the MDPH relied on the information provided
in the referenced documents and assumed that adequate quality assurance and
quality control measures were followed with regards to chain-of-custody, laboratory
procedures, and data reporting. The validity of the analysis and conclusions
drawn for this public health assessment is determined by the reliability of
the referenced information.

The analysis for metals of one pair of duplicate subsurface soil samples yielded concentrations
that varied by an order of magnitude or more. This suggests that there may have been some
interference with the analysis, and the results for all soil samples analyzed at the same time may
be questionable.

Access is not restricted at the outer perimeter of the site. Such restriction
would be impractical considering the large number of residences and businesses
within the site area. Individual businesses and residences are fenced for privacy
and security. The lagoons areas are not fenced, though the east lagoons area
is surrounded by operating industrial properties. The west lagoons area is located
a substantial distance from any residences or other facilities, except for the
wastewater treatment plant.

The former Scott Fetzer "Cyanide Destruction" facility is filled with debris
from collapsed buildings, and what buildings remain are in a state of imminent
collapse. The north side and part of the east and west sides of the facility
have long been fenced, but the remainder of the east and west sides and the
south side were not fenced, with free access from adjacent residential yards.
In May 1996, MDEQ removed one collapsing building from the property and installed
a new fence around the entire property.

To determine whether nearby residents are exposed to contaminants migrating
from the site, the Agency for Toxic Substances and Disease Registry (ATSDR)
evaluates the environmental and human components that lead to human exposure.
An exposure pathway contains five major elements: a source of contamination,
transport through an environmental medium, a point of exposure, a route of human
exposure, and an exposed population.

An exposure pathway is considered a completed pathway if there is evidence that all five of these
elements are or have in the past been present. A pathway is considered a potential pathway if one
or more of these elements is not known to be or have been present, but could be or have been.
An exposure pathway can be eliminated from consideration if one of the elements is not present
and could never be present. The following sections discuss the most important exposure pathways at this site.

Residents of the site study area have used water from private wells that was
contaminated with trichloroethylene, other volatile organic compounds (VOCs),
and metals. Alternative water supplies were provided to these residents and
the contaminated wells abandoned soon after the contamination was identified.
The records show that four private wells have been contaminated. From the normal
residential density of 3.8 per house, this means approximately 15 people would
have been exposed.

Surface soil

Soil at the former "Cyanide Destruction" facility and at the former L.A. Darling
property contain elevated concentrations of metals (Table
6). Access to these areas is not sufficiently restricted. There are reports
that children go onto the former "Cyanide Destruction" facility property freely.
There are 14 houses on the block adjacent to the "Cyanide Destruction" facility,
with yards contiguous to the facility grounds and no obstruction to traffic
between the facility grounds and the yards. The resident population adjacent
to the facility property, the people most likely to frequently go onto the site,
is estimated to be approximately 50 persons. People visiting these residences
might also occasionally visit the facility property.

VOCs present in the sludge and soil at the site might volatilize into interstitial
gas in the soil (soil gas), diffuse to the surface, and be carried by the wind
to neighboring residential areas. Alternatively, the contaminants might migrate
with the soil gas to nearby basements, diffuse through the walls or floor, and
collect in the confined space of the basements. The remedial investigation report
includes no results of ambient air, residential air, or soil gas sampling and
analysis in the site study area. The baseline risk assessment includes the results
of modeling of VOC emissions from the soils on-site, concluding that residents
in the site vicinity may incur a significant risk of both noncancer and cancer
adverse health effects (12). The assessors noted
that the calculation of the hazard for noncancer adverse health effects includes
a mathematical error that makes the hazard appear to be significant when the
hazard calculated without this error would not be significant.9
Such models are only as reliable as the calculations and assumptions they are
based on.

Surface water and sediment

Water and sediment in County Drain #30 contain VOCs, polychlorinated biphenyls,
polycyclic aromatic hydrocarbons, other semi-volatile organic chemicals, and
metals at concentrations in excess of the ATSDR comparison values. Access to
the drain, which is an open creek or ditch in the site area is not restricted.
The Michigan Department of Community Health has not heard any report of children
playing in the drain; however, the drain could attract children from the area
for their play.

The primary benchmarks against which exposures are evaluated for their potential
for causing noncancer adverse health effects are the minimal risk levels (MRLs),
developed by the Agency for Toxic Substances and Disease Registry (ATSDR), and
reference doses (RfDs) and reference concentrations (RfCs), developed by the
Environmental Protection Agency (EPA). It is generally accepted that a person
exposed to a dose of a chemical less than an MRL, RfD, or RfC is not likely
to experience non-cancer adverse health effects. The MRLs, RfDs, and RfCs are
lower than the observed threshold exposures, with safety factors included to
allow for different responses between species and between individuals. However,
these values may not be protective for individuals who are hypersensitive to
chemical exposures, including the very young, the very old, individuals whose
bodies are under stress from illness, and individuals who have an allergic response
to the chemical.

Threshold exposures from which MRLs, RfDs, and RfCs are derived may also be
cited if none of the derived values are available. The threshold exposures include
lowest-observed-adverse-effect levels (LOAELs) and no-observed-adverse-effect
levels (NOAELs). In a given experiment, with exposure route, species, and health
effect specified, the LOAEL is the lowest exposure at which the effect was observed,
and the NOAEL is the highest exposure at which no effect was observed.

For chemicals that may cause cancer, the risk associated with an exposure is
evaluated separately from noncancer health risks, using published potency factors,
which relate the chance of contracting cancer to the dose of the chemical. For
this assessment, the risk of cancer is considered significant if 1 extra case
of cancer is likely to develop among 1,000,000 people subject to the exposure
over their lifetimes.

Exposure doses for this assessment are computed using the following standard assumptions (10):
an adult weighing 70 kilograms (154 pounds) who drinks 2 liters (approximately 2 quarts) of
water a day and incidentally ingests 100 milligrams of soil per day; a child weighing 10
kilograms (22 pounds) who drinks 1 liter (approximately 1 quart) of water per day and
incidentally ingests 200 milligrams of soil per day, or, if subject to pica behavior, deliberately
ingests 5,000 milligrams of soil per day. Pica behavior is an abnormal urge to consume non-food
substances, such as soil, that most commonly occurs between ages 2 and 5.

Our evaluation estimates exposures to contaminants in the groundwater from the maximum
concentrations found in water from residential wells in the site study area (Table 4). Higher
concentrations of some contaminants were found in water from monitoring wells closer to the
source areas than the private wells (Table 5), however, since the contaminated private wells were
removed from service when the contamination was detected, people are not likely to be exposed to those levels of contaminants.

The time during which a private well user might have used contaminated water
from their well is difficult to estimate for three of the four contaminated
private wells at the site. For RW-1, RW-3, and RW-4, the sampling that found
the contamination was the first sampling of water from the well on record. Water
from RW-2 contained no organic contaminants when it was sampled in September
1988, January 1989, and September 1989, but the well was found to be contaminated
in July 1993. The residents were then advised to not use the water from their
well. A well at a neighboring house (RW-3) had been found to be contaminated
in December 1988. The documented exposure of the people who used water from
RW-2 lasted for not more than 4 years.

Volatile chemicals in water tend to evaporate when the water is used for showers,
washing, and other household uses. A person taking a shower using water contaminated
with volatile chemicals can inhale the volatilized chemicals, and thereby can
be exposed to as much of the chemicals as they would ingest while consuming
the water. Calculation of inhalation exposures to VOCs during showering are
estimated from the model developed by Little, specifically the results of his
computations plotted in Figure 5 of his paper. The results were based on a 10
minute shower using 13.7 L/min. water (3.6 gallons/minute) (13).

Acetone

Anyone drinking the water from a residential well in the site study area or using the water for
showers might have ingested enough acetone to exceed the RfD for non-cancer adverse health
effects, but not enough to exceed the doses at which adverse health effects have been observed in
published studies on animals or humans. There is no information available that links exposure to
acetone with cancer (14).

Methyl ethyl ketone

No one is likely to have ingested enough methyl ethyl ketone (also known as
2-butanone or MEK) from the water from a residential well in the site study
area to exceed the RfD for noncancer adverse health effects. The MEK concentration
in the air of a shower using water from RW-1 might have exceeded the RfC for
noncancer adverse health effects, but would not likely have exceeded the levels
at which adverse noncancer health effects have been observed. No available evidence
available links exposure to MEK with cancer (15).

Trichloroethylene (TCE)

No one was likely to ingest enough TCE from the water from the residential
wells to exceed the MRL for noncancer adverse health effects from intermediate-term
exposure. The concentration of TCE in the air of a shower using residential
well water from the site study area might have exceeded the MRL for noncancer
adverse health effects, but not the levels at which adverse health effects have
been observed. The epidemiologic data on cancer incidence in humans exposed
to TCE are ambiguous. Some experimental animals whose food and water contained
TCE have developed liver cancer. EPA had classified TCE as a probable human
carcinogen (EPA Class B2), but has withdrawn the classification pending further
review (16). A lifetime's use of water, for either
drinking or showering, containing the concentrations of TCE in the residential
wells at the site would result in a low increased risk of contracting cancer.
The private wells were taken out of service and alternative water supplies provided
to the residents as soon as the contamination was detected. The residents would
not be likely to have used the wells for a long enough period to incur any increased
risk of contracting cancer from the TCE by either inhalation or ingestion.

Vinyl chloride

Anyone might have ingested enough vinyl chloride in water from a residential
well in the site study area to exceed the MRL for non-cancer adverse health
effects from chronic exposure by ingestion, but not enough of the chemical from
this residential well to exceed the doses at which adverse non-cancer health
effects have been observed. The concentration of vinyl chloride in the air in
the shower using water from that well would exceed the MRL for intermediate-term
exposure by inhalation, but would not exceed the levels at which adverse non-cancer
health effects have been observed in epidemiological or laboratory animal studies.
Some workers occupationally exposed to vinyl chloride developed liver cancer,
and some laboratory animals whose feed contained the chemical developed liver
cancer. The U.S. EPA has classified vinyl chloride as a known human carcinogen
(U.S. EPA Class A) (17). As of this writing, the
U.S. EPA is reviewing the cancer potency factor for vinyl chloride (18).
Based on the previously available potency factor, lifetime use of water containing
the concentration of vinyl chloride found at the site could result in a low
increased risk of contracting cancer through either ingestion or inhalation.
The one residential well that contained vinyl chloride when sampled was replaced
with an alternative water supply and the well abandoned. The residents of the
site study area were not likely to have used the contaminated water long enough
to incur any significant increased risk of contracting cancer or to incur any
noncancer adverse health effects.

1,1-Dichloroethylene

No one is likely to ingest enough 1,1-dichloroethylene from the residential wells at the site to
exceed the MRL for non-cancer adverse health effects. The air in a shower that used water from
the site would not be likely to contain enough 1,1-dichloroethylene to exceed the MRL for non-cancer adverse health effects. Some laboratory animals who breathed air, ate food, or drank
water containing 1,1-dichloroethylene contracted cancer of various organs. The U.S. EPA has
classified 1,1-dichloroethylene as a possible human carcinogen (U.S. EPA Class C) (19). A
person who drank water from the site area for his or her lifetime might ingest enough 1,1-dichloroethylene to incur a low increased risk of contracting cancer. He or she would not be
likely to inhale enough of the chemical during his or her showers to incur any increased cancer
risk. The residential well where the water contained 1,1-dichloroethylene has been replaced by a
connection to municipal water. The people who used that residential well would not be likely to have ingested enough of the chemical to incur any apparent increased cancer risk.

Metals in groundwater

A child might ingest enough arsenic from the residential wells on and near
the North Bronson Industrial Area (NBIA) site study area to exceed the MRL for
noncancer adverse health effects, but not enough of the metal to exceed the
concentrations at which adverse health effects have been observed. The scientific
literature includes epidemiological studies that indicate that people exposed
to high concentrations of arsenic in their food or water run an increased risk
of contracting cancer of the skin. The studies also linked exposure to arsenic
with increased occurrence of cancer of liver, lung, and bladder, though the
linkage has not been proven. EPA has classified arsenic as a known human carcinogen
(EPA Class A) (20). A person using groundwater
from the site area for their drinking water source for his or her lifetime might
ingest enough arsenic to incur a moderate increased risk of contracting skin
cancer. The arsenic concentrations found in the groundwater in the site area
are less than EPA's maximum contaminant level of 50 ppb. The arsenic is probably
of natural origin, and the concentrations found are not unusually high for that
part of Michigan.

No one is likely to ingest enough beryllium from the groundwater in the site
vicinity to exceed the RfD for noncancer adverse health effects. Some laboratory
animals whose diet contained beryllium developed lung cancer. EPA has classified
beryllium as a probable human carcinogen (EPA Class B2) (21).
A person whose water supply for his or her lifetime contains the beryllium concentration
found in the groundwater on and near the NBIA site study area might incur a
low increased risk of contracting cancer. None of the beryllium concentrations
in water from the residential wells exceeded the EPA MCL for the metal (4 ppb).

No MRLs or RfDs available for exposure to lead. The lead content of water from
residential wells in the site study area did not exceed the EPA proposed action
level for lead in drinking water (15 ppb), though the concentration in a monitoring
well did. A child whose drinking water contained the lead concentration found
in that monitoring well might ingest enough of the metal to attain the dose
at which people dosed with lead acetate for a period of 7 weeks experienced
decreases of the activity of enzymes involved in blood synthesis. Laboratory
animals whose food or water contained similar amounts of lead for their body
weight suffered neurological problems. Lead is known to contribute to neurological
and developmental problems in children, but the presence of other sources of
the metal in the environment and the metal's tendency to accumulate in the body
complicate the evaluation of a specific exposure. Some laboratory animals whose
diet or water contained lead developed kidney cancer. The U.S. EPA has classified
lead as a probable human carcinogen (EPA Class B2). Not enough evidence is available
to evaluate the cancer risk from exposure to lead (22).

A child might ingest enough manganese from the water in the residential or municipal wells in
and near the site study area to exceed the RfD, but not sufficient to exceed the doses at which
non-cancer adverse health effects have been observed. There is no evidence available linking
exposure to manganese with cancer (23).

Metals in surface soil

A child subject to pica behavior10
might ingest enough surface soil from the site study area to exceed the MRLs
or RfDs for any of the metals present. The pica child would not be likely to
ingest enough of the metals present to attain the doses at which adverse health
effects have been observed in laboratory animals (20,
21, 22, 23,
24, 25, 26,
27, 28, 29,
30, 31, 32,
33). However, lead is a cumulative poison, and
long-term exposure to low levels can result in adverse health effects. The lead
concentrations found in the surface soil on the site are within the range commonly
found in urban areas (22) and less than the health-based
clean-up level for lead in soil (400 ppm) developed by the Michigan Department
of Environmental Quality (MDEQ) under provisions of the Michigan Environmental
Response Act (Public Act 451, Part 201, as amended). Lifetime exposure to the
concentrations of arsenic and beryllium present on the site might result in
a low increased risk of contracting cancer (20, 21).
The other carcinogens present, cadmium, chromium(VI), and nickel, have primarily
been recognized as carcinogens through inhalation, and there is not sufficient
information to evaluate the cancer risk from other pathways of exposure (24, 25, 26).
Chromium(VI) compounds tend to be reduced to chromium(III) compounds in the
environment (24), though no information is available
as to which chromium species are present at the site.

Contaminants in sediments in County Drain #30

A child playing in County Drain #30 near the site one day a week might incidentally
ingest sediments that contain enough cadmium to exceed the MRL for chronic exposure
and enough chromium to exceed the RfD for chromium(VI), but not enough of either
metal to exceed the LOAELs (24, 25).
Cadmium and nickel have primarily been recognized as carcinogens through inhalation,
and information is insufficient to evaluate the cancer risk from other pathways
of exposure (25, 26).
Chromium(VI) compounds tend to be reduced to chromium(III) compounds in the
environment (24), though no information is available
about which chromium species are present in the sediment.

No one is likely to spend enough time in the ditch over a lifetime that incidental ingestion of
sediments would result in a significantly increased risk of contracting cancer from any of the
contaminants for which cancer slope factors are available.

Lead is a cumulative poison, and long-term exposure to low levels can result in adverse health
effects. The lead concentrations found in the sediment are within the range commonly found in
urban areas (22) but exceed than the health-based clean-up level for lead in soil (400 ppm)
developed by the MDEQ under provisions of the Michigan Environmental Response Act (Public
Act 451, Part 201, as amended).

Various polycyclic aromatic hydrocarbons (PAHs), including acenaphthylene,
benzo(a)anthracene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(g,h,i)perylene,
benzo(a)pyrene, chrysene, dibenzo(a,h)anthracene, indeno(1,2,3-cd)pyrene, 2-methylnaphthalene,
naphthalene, and phenanthrene, were found in samples of sediments from County
Drain #30. MRLs and RfDs for noncancer adverse health effects are not available
for these PAHs. PAHs are ubiquitous in the environment, as products of incomplete
combustion. The concentrations found in the sediments were generally within
the range found in urban soils (Reference 11, Table
5-2), and it is not likely that any significant increase in adverse health effects
would result from exposure to the sediments. EPA has classified benzo(a)anthracene,
benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene, chrysene, dibenzo(a,h)anthracene,
and indeno(1,2,3-cd)pyrene as probable human carcinogens (EPA Class B2). Animals
whose food contained these PAHs or who had the chemicals applied to their skin
for long periods developed cancer. Incidental ingestion of sediments from the
creek would not result in any significant increased risk of contracting cancer
(11, 34). Laboratory
animals who developed cancer when PAHs were applied to their skin were exposed
to either the pure chemicals or comparatively high concentrations in liquid
solvents. No evidence is available that skin contact with soil containing the
PAH concentrations generally found in the environment, such as those found in
the sediments of County Drain #30, poses any significant increased risk of contracting
cancer.

Volatile organic chemicals in basement air

No data are available on the concentrations of organic chemicals in ambient
air at the site. As an upper-limit, worst-case scenario, the following discussion
considers the concentrations of the various chemicals present in the water that
would be present in air in equilibrium with the water. These are the concentrations
that would be in the air in a closed container that also contains water containing
the highest concentrations of VOCs found in groundwater in the site study area.
This is the highest possible concentration of the chemicals in the air or in
soil gas at the site. In the open air, those concentrations would only be found
at the surface of the water. Diffusion and dispersion involved in the movement
of gases through the soil and into the air will greatly reduce the concentrations
encountered in the ambient air. The air of a confined space such as a basement,
where the chemicals have not had the opportunity to disperse, might contain
the chemicals at concentrations comparable to the equilibrium level.

The concentration of vinyl chloride in air in equilibrium with the groundwater
in the site study area, as might be found in a basement, might exceed MRLs and
the levels at which decreased longevity, minor changes in various organs, and
increased rates of cancer were observed in laboratory animals who breathed the
air for 2 weeks or more. Breathing this air for a lifetime might result in an
extremely high increased risk of contracting cancer (17).
The concentrations of 1,2-dichloroethylene and trichloroethylene in air in equilibrium
with the groundwater might exceed available MRLs, though the concentrations
would not be likely to exceed the levels at which adverse health effects have
been observed (16, 35).
Breathing air with this concentration of trichloroethylene for a lifetime might
result in a very high increased risk of contracting cancer (16).
Other VOCs present in the groundwater would not likely be in the air at concentrations
above available MRLs, levels at which adverse noncancer health effects have
been observed, or that would result in more than a low increased cancer risk
(19, 36, 37, 38, 39).
As described previously, these conclusions are based on the highest possible
concentrations in the air, and dispersion through the soil and air would likely
reduce the concentrations people would be exposed to. Actual data on basement
air concentrations are needed to accurately evaluate the health hazard.

The baseline risk assessment in the remedial investigation (RI) includes calculations
based on a mathematical model for the emission of VOCs from the subsurface soil
at the site. The modeled concentration of methylene chloride, calculated for
a point 100 meters downwind of the eastern lagoons as given in Table B-12 in
Reference 12, exceeds the intermediate-term inhalation
exposure MRL for noncancer adverse health effects, but not the concentrations
at which adverse health effects have been observed (36).
None of the other concentrations in Table B-12 in Reference 12
exceed available MRLs, RfCs, or levels at which adverse noncancer health effects
have been observed (14, 15,
16, 36, 40,
41, 42, 43).
Among the VOCs found in the soil samples, chloroform, methylene chloride, and
trichloroethylene are or have been classified as probable human carcinogens
(EPA Class B2) (16, 36, 40).
Living 100 meters downwind of the eastern lagoons for a lifetime might result
in a low increased risk of contracting cancer.

A resident of Bronson has expressed concern about a perceived high rate of
cancer within the city. The Michigan Department of Community Health (MDCH) Environmental
Epidemiology Division has requested cancer incidence data for the city of Bronson
from the MDCH Office of the State Registrar and Division of Health Statistics.

It was reported that a resident of the site study area whose private well was contaminated has
contracted cancer. A MDCH toxicologist spoke to the resident regarding the possible association
between the contaminants in the groundwater and her illness. He was unable to determine if her
exposure to contaminated groundwater caused her illness.

Because fewer than half a dozen private wells were affected by contaminated groundwater, it is
not possible to evaluate the relationship between exposure to contaminants at this site and
disease incidence with any statistical confidence in the results.

1. The Scott Fetzer "Cyanide Destruction" facility is dangerous. It should be fenced
or cleaned up.

MDCH agrees that the facility is dangerous, both from the physical hazard and
from the chemical contamination present. Michigan Department of Public Health
(MDPH) staff present at the June 15, 1995, Michigan Department of Natural Resources
(MDNR) public meeting (Brendan Boyle, Michelle Borgialli, and John Filpus) strongly
supported MDNR efforts to restrict access to the "Cyanide Destruction" facility
or to have it cleaned up promptly.

2. Our city water has a lot of iron in it.

MDPH Division of Water Supply personnel report that the Bronson municipal wells have had a
history of elevated iron, hardness, and (occasionally) nitrate levels. High concentrations of iron
in drinking water are not considered to be hazardous to human health, though the metal can make
the water unsightly, give it a poor taste, discolor fixtures, or interfere with the operation of water
heaters and softeners. Bronson voters had rejected a proposal to fund an iron-removal system for
their water treatment plant. The occasional high nitrate concentrations have been attributed to a
source near one of the existing city wells, and the city controls the nitrate level in the water
system through adjusting the pumping rates of the wells. Water from the system is sampled and
analyzed for nitrates every quarter (last sampled in late 1995).

Water from the system is also tested every month for bacteria, every year for
lead and copper (last sampled in the summer of 1995), and every 3 years for
VOCs (last sampled in 1992, a new sample should be collected soon, as of January
1996). Except for iron, hardness, and nitrates, none of the analyses have found
any parameter above the EPA's Safe Drinking Water Act standards, either the
MCLs, based on health concerns, or the secondary MCLs, based on other aesthetic
considerations such as appearance, odor, and taste. The city's well #3, located
within the boundaries of the NBIA site study area, has been abandoned and is
no longer in use. Their two remaining wells are east of the town and upgradient
of the contamination at the NBIA site (5).

3. Can the chemicals in the soil and groundwater affect the vegetables in our gardens?

Most garden plants rely on rain for their water needs. Their root systems are
not extensive enough to reach groundwater in most places. Contamination of food
plants is most likely to occur through contamination in the soil or in irrigation
water. The questioner uses municipal water on the garden, which eliminates that
possible route for contamination. There is no information on whether the soil
in residential areas of the site study area is contaminated; however, the soil
at the "Cyanide Destruction" facility is contaminated with various metals. Some
contamination from the facility may have migrated to neighboring residential
yards, including that of the questioner. Of the metals found in the soil of
the facility, enough cadmium is known to be taken up by plants such that the
concentration in the plants could reach a potentially hazardous level. The baseline
risk assessment includes estimations of the health risk from eating plants that
had grown in soil at the site. MDCH accepts this analysis and concurs with the
conclusion that the risk is not significant, especially considering that the
concentrations of the metals are likely to be much lower in gardens off the
site than in the soil on the site (12).

4. What are the type of health effects that could result from the type of contamination in our well?

We are concerned about the chemical contamination found in the water from some
residential wells within the site study area. The published scientific literature
links exposure for long periods of time to large amounts of several of the chemicals
found in the water with liver damage, anesthetic effects, and liver cancer in
people or animals. The hazard to public health posed by any environmental contaminant
depends upon the amount of the contaminant people are exposed to and the time
the exposure lasts. As described in the Toxicological
Evaluation section above, the amounts of contaminants detected
in the water from those wells have generally not been seen to cause adverse
health effects in people or animals in various health studies. The evaluation
of cancer risks in this document assumes that there is no exposure to a carcinogen
that does not increase the risk of contracting cancer. As described previously,
the increased risk of contracting cancer is considered significant in this evaluation
if a lifetime exposure is calculated to result in 1 excess cancer case in 1
million people exposed. This threshold is much less than the roughly 1 in 4
to 1 in 3 lifetime cancer rate for the general U.S. population. It is generally
very difficult to attribute a case of cancer to a specific exposure to a carcinogen,
particularly when the population exposed is small. In addition, the contaminated
wells were promptly taken out of service when the contamination was discovered,
which would reduce the risk incurred. For more details see the Toxicological
Evaluation section.

5. Is our water safe to drink?

In general, groundwater outside the site study area is safe to drink. The only
residential wells that have contained contaminants at concentrations considered
to be unsafe for consumption have been taken out of service. Some residential
wells have contained lead, arsenic, and other metals at concentrations that
are above the comparison values ATSDR uses to select contaminants for further
evaluation but below EPA's maximum contaminant levels (MCLs) or action levels
established for drinking water quality. The MCLs and action levels are generally
considered safe for drinking water consumption.

If you are still concerned, contact your local health department to make arrangements to have your water sampled and analyzed.

6. [I am] very concerned about water [and] live by a ditch with contaminated water.

ATSDR and MDCH share your concern about the contaminated water and sediment
near your home. We support and encourage the efforts by EPA and MDNR/MDEQ to
eliminate the contamination. If you are concerned about the contamination, the
first step you should take is to avoid contact with the ditch. There is nothing
in the water or sediments that is likely to harm you unless you ingest it or
come into direct contact with it. The concentrations of the contaminants in
the water and sediments are low enough that only continuous or regular contact
over a long time is likely to result in adverse or harmful health effects. To
reduce the chance for children coming into contact with the contaminated water
and sediment, we are proposing to post warning signs at the access points to
the ditch.

The MDCH released a draft of this assessment for public comment on November
6, 1996. The comment period lasted until December 6, 1996. Comments received
and MDCH responses are listed in the Responsiveness
Summary at the end of the document.